Sweden risks messy parliamentary situation after the election.

The United Minds-Cint poll, published in the Aftonbladet daily, handed the Sweden Democrats (SD) a record 6.5 percent support -- well above the four percent threshold for entering parliament.

Nearly 46 percent of people intended to vote for the ruling centre-right coalition while 45 percent said they would vote for the left-wing opposition coalition, the poll of 2,004 people between July 12 and August 1 showed.

With less than a percentage point difference between the two main blocs, the right-wing SD party, which has never before made it into parliament, would likely become the kingmaker of the election, observers said.

"It is probable that we will have a very messy parliamentary situation after the election," Carl Melin of United Minds told the paper.

The four parties in the centre-right coalition and the three main leftist opposition parties have ruled out cooperating with SD but observers say it could be difficult to block the far-right party from the decision-making process.

The Sweden Democrats leader, Jimmie Åkesson, said he was convinced the two main blocs would rethink their stance as his party gains in popularity.

"They don't want to give up their power in the parliament, that is what is most important for them," he told the news agency TT.

If either bloc manages to secure a parliamentary majority, SD would not make much difference, political scientist Peter Santesson-Wilson of the Ratio research institute in Stockholm told AFP.

However, "a minority government would be very unstable if it refused to ever vote with (SD)," he said, pointing out that the party could for instance choose to vote on the opposition's, rather than the minority government's, budget proposal.

"That would cause political chaos and the government would quickly be forced to resign," he said.

The Sweden Democrats won just 2.9 percent of the vote in the country's last elections in 2006. The party argues that Sweden should remain a "homogeneous society" by drastically cutting the numbers of immigrants.